Meteorological reanalysis models provide hourly snapshotsof the state of the atmosphere over an extended period oftime, typically since the dawn of the satellite era (1970s). Incontrast to the operational weather forecast models on whichthey are based, reanalysis models focus on historical weather.From these historical snapshots a continuous weather timeseries can be assembled for all locations on Earth. For thepurposes of ASHRAE, these “virtual” weather stations canthen be used in the absence of more conventional stations, e.g.in the so-called “data deserts” found worldwide, to calculatedesign climatic conditions or as input to building simulationsoftware. However, these virtual stations, being model-based,may not reflect the reality on the ground, putting buildingdesign at risk. ASHRAE thus sponsored a research project(1745-RP) to evaluate the feasibility of the use of reanalysesby its members. This paper provides some of the highlights ofthe project and provides general recommendations, warnings,and guidelines, for the use or reanalysis for building design.